/*
 * Copyright (C) 2025 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.cloud.teleport.spanner.spannerio.changestreams.mapper;

import com.google.cloud.spanner.Dialect;
import java.io.Serializable;

/**
 * Factory class for creating instances that will map a struct to a connector model. The instances
 * created are all singletons.
 */
// transient fields are un-initialized, because we start them during the first fetch call (with the
// singleton pattern)
@SuppressWarnings({"initialization.fields.uninitialized", "initialization.field.uninitialized"})
public class MapperFactory implements Serializable {

  private static final long serialVersionUID = -813434573067800902L;

  private transient ChangeStreamRecordMapper changeStreamRecordMapperInstance;
  private transient PartitionMetadataMapper partitionMetadataMapperInstance;
  private final Dialect spannerChangeStreamDatabaseDialect;

  public MapperFactory(Dialect spannerChangeStreamDatabaseDialect) {
    this.spannerChangeStreamDatabaseDialect = spannerChangeStreamDatabaseDialect;
  }

  /**
   * Creates and returns a singleton instance of a mapper class capable of transforming a {@link
   * com.google.cloud.spanner.Struct} into a {@link java.util.List} of {@link
   * com.google.cloud.teleport.spanner.spannerio.changestreams.model.ChangeStreamRecord} subclasses.
   *
   * <p>This method is thread safe.
   *
   * @return singleton instance of the {@link ChangeStreamRecordMapper}
   */
  public synchronized ChangeStreamRecordMapper changeStreamRecordMapper() {
    if (changeStreamRecordMapperInstance == null) {
      changeStreamRecordMapperInstance =
          new ChangeStreamRecordMapper(this.spannerChangeStreamDatabaseDialect);
    }
    return changeStreamRecordMapperInstance;
  }

  /**
   * Creates and returns a single instance of a mapper class capable of transforming a {@link
   * com.google.cloud.spanner.Struct} into a {@link
   * com.google.cloud.teleport.spanner.spannerio.changestreams.model.PartitionMetadata} class.
   *
   * <p>This method is thread safe.
   *
   * @return singleton instance of the {@link PartitionMetadataMapper}
   */
  public synchronized PartitionMetadataMapper partitionMetadataMapper() {
    if (partitionMetadataMapperInstance == null) {
      partitionMetadataMapperInstance = new PartitionMetadataMapper();
    }
    return partitionMetadataMapperInstance;
  }
}
